The present invention relates to animal litter and, more particularly, compositions for animal litter and methods of making animal litter.
Many different types of absorbant substances are used as animal litter including recycled newspaper, paper sludge, wheat, soybeans, ground corn cob granules, rice hulls, peanut hulls, sunflower hulls, cedar, sawdust and other organic materials. Clay, however, is the most common form of animal litter, e.g., used as cat litter, on the market making up to 80% to 90% of the litter market.
Clay based litter is available in either sand-like clumping or non-clumping gravel-like forms. Clumping clay litter contains sodium bentonite, a particularly absorbant type of clay (a gelling clay) which forms clumps after contacting animal urine and then can be scooped out of the litter pan to reduce odor from urine. More litter must be added to replace the litter that was thrown away. Advantageously, not all the litter has to be thrown away at the same time, and therefore it is economical, as less litter is needed.
In comparison, non-clumping litter does not form clumps when in contact with urine. The solid feces must be picked out and thrown away regularly but, at some point, the entire litter must be thrown out as urine accumulates at the bottom of the pan and the odor becomes objectionable over time. Because urine collects at the bottom of the pan, non-clumping clay litter does not last as long compared to clumping clay litter and non-clumping clay litter becomes objectionable more quickly, as it cannot be scooped out.
Clay-based animal litters present several disadvantages. Clays contain silica (silicon dioxide) dust that may be harmful to the health of animals, e.g., felines, and humans when inhaled. Prolonged inhalation of silica dust, which contains crystalline silica, can lead to silicosis, a respiratory disease caused by the inhalation of silica dust, which can cause scar formation within lung tissue and can obstruct the flow of oxygen into the lungs and bloodstream.
When clumping clay is used, the clumps formed by absorption of urine must be thrown out daily, in addition to removing the solid feces in the litter. The clumps may fall apart during removal and thus require some additional effort. With any clay based litter, odor is often objectionable after only a few days as urine pools at the bottom of the litter pan and causes the litter to stick to the pan. Use of clay also has some other disadvantages. Clay is a non-renewable resource usually obtained by stripping land and thus causing scarring of land. The U.S. Bureau of Mines estimates that in 1994, approximately 1.5 million metric tons of clay were mined to make absorbent cat litter and much of it was stripped mined. Clay is heavy and dense and as a result, lifting a litter pan filled with clay litter can be inconvenient or difficult for some individuals.
A major problem with clays and most other litter materials is the odor that is associated with ammonia present in urine. Urine is often coated over the outer surface of the litter material rather than absorbed within the material. As a result, the odor is volatilized into the air. The problem of odor emanating as a by-product of urine and fecal matter has been dealt with in many ways. Odor masking agents have been used to hide odors. See for example, U.S. Pat. Nos. 4,020,156 to Murray et. at and to U.S. Pat. No. 4,085,704 to Frazier. Both patents are herein incorporated by reference. Disadvantageously, the methods disclosed in these patents merely mask but do not eliminate the odor.
Another approach taken is to kill the microorganisms that create odors. This approach is taken in U.S. Pat. Nos. 4,607,594; 4,930443; 4,607,594; 5,005,520; and 5,507,205, all of which patents are herein incorporated by reference.
More recently, silica gel has been used as animal litter. See, for example, U.S. Pat. No. 5,970,915, which is herein incorporated by reference in its entirety. Silica gel can adsorb its weight in moisture and with some types of silica gel up to twice their weight. Silica gel adsorbs moisture from the urine, thereby helping to eliminate the odor produced by the presence of urine. Advantageously, silica gel may be flushed in small amounts and it will not clog septic systems.
A significant problem, however, with the use of silica gel is its relatively high cost compared to other types of litter material. It should be emphasized that silica gel does not contain the type of harmful silica found in clay. Instead, silica gel is an amorphous form that is essentially chemically inert and relatively non-toxic. Some animal litters use solely silica gel. Such a purely silica gel animal litter is relatively costly compared to other types of animal litters.
U.S. Pat. No. 6,578,521 to Raymond, et al., was granted for a litter composition comprising a mixture of absorbant material and silica gel. The '521 patent describes the use of clay and silica gel composition or mixture. A major disadvantage of a clay and silica gel animal litter is that it still employs clay. Absorbant clay is a non-renewable resource, which is mined, dried and ground to a desirable consistency. Clay contains crystalline silica which is a known carcinogen, according to the California EPA. Dust controlling agents are often added by the manufacturer to control the dust. Even with dust controlling agents added, it is nevertheless dusty and heavy, even at 50% weight of the total litter. Regardless of the weight mixture, any combination of silica gel and clay will be dusty and will be tracked on the animals feed and, moreover, breathing such dust whether silica gel or silica from the clay, into animal or human lungs is undesirable.
What is needed is a cat litter that is effective, economical, and yet safer to humans and animals than clay-based litters.